A conventional integrated circuit probe station designed for engineering use, e.g., device characterization, as opposed to testing of integrated circuit devices on a production basis, comprises a stationary table on which an integrated circuit chip is positioned and a probe that is movable relative to the table for bringing contact elements of the probe into electrically-conductive contact with the contact pads of the chip. The probe may be a ceramic probe of the kind described in U.S. patent application Ser. No. 672,846 filed Nov. 16, 1984. In two practical implementations of a probe station employing ceramic probes of this kind, several probes are mounted on a support structure and are movable relative to each other along the X and Y (horizontal) axes to position their respective contact elements in a pattern corresponding to the pattern of the contact pads of the chip under test, and are movable relative to each other along the Z (vertical) axis to position the contact elements in a common plane. When the probes have been properly positioned on the support structure, the support structure is, in one implementation, moved horizontally, e.g., using two-axis micrometer screws, in order to align the contact elements of the probes with the contact pads of the chip under test. In the other implementation, the probe support structure remains stationary and the chip under test is moved in the horizontal direction on a grease plate. In each case, the support structure is then lowered in order to establish physical contact between the contact elements of the probes and the contact pads of the chip. This technique has proved troublesome because the support structure for the probes is difficult to machine accurately, and therefore it is difficult to achieve precise coplanarity of the contact elements of the probes, and moreover the support structure is heavy and bulky and therefore it is difficult to move the support structure precisely in the vertical direction. Because of the first factor, one or more of the contact elements of the probes may not touch the contact pads of the chip under test with sufficient force to establish electrical contact, or may not touch the contact pads at all. If the operator attempts to cause the support structure to move farther in the vertical direction, so as to achieve the desired contact with all contact elements, the second factor limits the precision with which the support structure can be moved, with the result that one or more of the ceramic probes may be deflected to an excessive extent due to contact force between the contact elements of the probe(s) and the contact pads of the chip, and be broken. Moreover, the nature of the support structure is such that upon movement of the support structure in the vertical direction, the coplanarity of the contact elements may be disturbed.
The Electroglas Model 1034X autoprober has table defining a horizontal surface over which a probe is mounted so that it remains stationary in use. A wafer chuck is moved over the table using two-axis stepping motors to bring the contact pads of a chip on the wafer chuck into position underneath the contact elements of the probe. When the wafer chuck is properly positioned in the horizontal direction, a Z-axis stepping motor is used to raise the chip and establish physical contact between the contact pads of the chip and the contact elements of the probe. Initial positioning of the wafer chuck is achieved manually, by use of a joystick that is coupled to X and Y axis pulse generators for generating pulses to drive X and Y axis stepping motors. After initial positioning has been achieved, the chuck is advanced to successive die sites automatically, without operator intervention.